Organic electroluminescent display panel, as a novel flat panel display device, has the advantages of self-luminescence, low cost, fast response speed, wide visual angle, low power consumption, high brightness, wide range of working temperature, being applicable for flexible display and simple manufacturing process, etc., thus it has a wide application prospect.
A conventional organic electroluminescent element generates electroluminescence due to a multi-layer structure thereof, which includes an anode layer, a cathode layer and an organic electroluminescent material layer arranged therebetween. Based on the materials used, the organic electroluminescent element may be divided into two types: one is a small molecule light-emitting diode mainly made of a dye or a pigment, which is referred to as Organic Light-Emitting Diode (OLED) or Organic Electroluminescence (OEL); and the other is a polymer light-emitting diode mainly made of high molecules, which is referred to as Polymer Light-Emitting Diode (PLED) or Light-Emitting Polymer (LEP). In addition, based on the color of light emitted by the organic electroluminescent element, the organic electroluminescent material layer may mainly be made of three materials, i.e., RED (R), Green (G) and Blue (B) materials. In order to realize full-color display, each pixel unit of the organic electroluminescent display panel includes RGB subpixel units, and an organic electroluminescent element that emits the light in a single color corresponds to a subpixel unit.
A film deposition method for the organic electroluminescent display device mainly includes vacuum evaporation processing and solution processing. The vacuum evaporation processing is applicable for organic small molecules, and as a relatively mature technology, it is able to improve the evenness of a film. However, it also has the disadvantages of large investment for equipment, low utilization rate of material and low precision of mask alignment for large-sized products. Additionally, the solution processing includes spin coating, ink-jet printing, nozzle coating, etc., and it is applicable for polymer materials and soluble small molecules. Moreover, it has the feature of low equipment cost, so it is especially advantageous to large-scale production as well as large-sized products.
For the vacuum evaporation processing, although it has been employed in the mass production for small and medium-sized organic electroluminescent display devices, the resolution thereof cannot match a liquid crystal display (LCD). In the production of large-sized organic electroluminescent display devices, because the precision of mask alignment is low in the manufacture process of subpixel units, it is difficult to achieve the mass production. In addition, for the solution processing, although prototypes for large and small-sized organic electroluminescent display devices appear continuously, the mass production thereof does not begin yet. Further, as limited by the precision of the film-forming equipment, the resolution thereof is not high.
Thus, it is difficult in the OLED industry to manufacture an OLED device with a high resolution. At present, although there exist many different pixel designs, i.e., the well-know pixel arrangement modes such as square, side by side, pentile and stripe, these pixel designs are only limited to changes in the arrangement modes of the pixels themselves, and the actual resolution thereof is not improved greatly. At the same time, with respect to the film-forming technology related to finely-patterned thin film transistors, due to limitations in the process and equipment, it is difficult for the vacuum evaporation processing and the solution processing to manufacture the organic electroluminescent display device with a high-precision pattern.